During the second half of the 20th century, a large number of psychological theories of intellectual styles were developed. The term intellectual styles is an umbrella term proposed by Zhang and Sternberg (2005) to unify 10 theoretical frameworks of style, and it is gaining increasing use as an encompassing term for theories of cognitive, personality, learning, teaching and thinking styles, etc. In 1984 Messick (1984) stated that more than 19 cognitive styles could be defined at his time of writing. Seven years later, Riding and Cheema (1991) identified more than 30 different constructions of theories of styles designated cognitive styles or learning styles. In more recent reviews, the stated number of style theories is considerable higher, but also, in most cases, subject to a greater degree of uncertainty in labeling theories as theories of cognitive, learning, teaching, personality style, etc., and in some cases also a looseness in distinguishing theoretical models (or conceptual frameworks) from instruments. In an investigation of the applicability of learning style theories, Coffield et al. (2004) claimed to identify 71 theories of learning styles. In connection with Nielsen’s (2012) historical review of the styles literature, the count of what was referred to as style theories/conceptual models of styles, in 488 articles, reached 78, and 208 different instruments for the measurement of styles were referenced. However, the numbers can be expected to be somewhat, if not substantially larger, as the 488 articles reviewed in detail belonged to a larger pool of articles on styles (N = 2931). Evans and Waring's (2012) review of applications of styles in educational instruction and assessment identified 84 differently named style models.
Based on information such as the above, practitioners may be tempted to believe that a rapid development of style theories has been taking place, and indeed new theories (and instruments) have been developed through the years and are still being developed. However, the situation behind the number of theories in the different reviews is more a mixture of development of new theories, and the fact that the different reviews and summary works define both the overall concept of styles as well as the more specific style concepts in different ways. These differences in definitions are more often than not subtle – and as such elusive to the practitioner – but can have a big impact on the number of theories claimed to be theories of styles, as well as the number of theories claimed to specifically be theories of learning styles, cognitive styles, etc. For example, at the general level, at least one of Coffield et al.'s (2004) acclaimed theories of style was not as such a style theory, but rather a categorization model of style theories (i.e. Curry's onion model 1981). Another example at the general level, is the more recent article by Kozhevnikov et al. (2014), where the concepts of extrinsic-intrinsic motivation and tolerance for ambiguity were, quite unusually, claimed to be styles. An in depth look at the included reviews does, however, also show disagreement as to whether a number of other individual difference constructs are indeed style concepts or other types of individual differences, such as personality, ability and preferences for certain career fields or jobs (i.e. the Myers-Brigs personality types, Witkin's field-dependence/field-independence, Holland’s career-personality types).
Adding to the difficulties facing practitioners wanting to find a suitable theory of styles to apply in their own field of work are the many disagreements on the overall orientation or nature of the styles (for example cognitive or personality oriented styles) across the many different theories. Depending on the review or summary work consulted, a single theory may be categorized as a theory of cognitive styles in one review and a theory of personality styles in another review. Nielsen (2012) determined clearly that both theories and instruments were labeled somewhat arbitrarily as theories/instruments of learning, cognitive or teaching styles, in 488 articles reviewed in detail.
It is evident that the disagreements on the general as well as the more specific definitions of styles in the field have lead to many different categorizations of style theories based on different sets of criteria. Such disagreements are, of course, fruitful within the field of style theory and research as they stimulate further discussion, ideas and development. However, the same disagreements and the resulting different categorizations of theories of styles may very well have negative consequences for the intended fields of application of the theories and the associated instruments for measuring styles, because practitioners seeking the theory and instrument best suited for their intended use/application simply cannot find their way through this jungle of disagreements. Or worse still, the practitioners might not realize that it is a jungle, because as the concepts being used in reviews, which have sought to categorize and give an overview of the styles field, are the same word-wise, but defined quite differently, the resulting categorizations have appeared to be more alike than they really are.
The aim of the present study is to aid practitioners in finding some paths through this jungle and in choosing the "right" theory and measurement of style for their intended practical purpose. This will be achieved through a detailed analysis of a number of existing reviews and summary works, which categorize style theories, and placing these categorizations into a new proposed taxonomy for the organization (or categorization) of style theory categorizations, with three main types of categorization. This analysis will bring forward commonalities and differences between the different theory categorizations, thereby providing practitioners with useful information. That is, information on practice-related core concepts such as overall orientation of theories (cognitive, personality and/or learning/teaching styles), as well as stability and pedagogical amenability, which can aid the practitioner in his/her search for an appropriate theory within their intended area of use/application.
The included reviews and summary works
The included reviews and summary works (Curry 1981; Messick 1984; Schmeck 1988; Jonassen and Grabowski 1993; Rayner and Riding 1997; Sternberg and Grigorenko 2001; Coffield et al. 2004; Zhang and Sternberg 2005) were, all but one, chosen as they are much cited and influential reviews or summary works in the styles field, when it comes to determining the specific nature of styles (i.e. categorizing style theories) as cognitive, learning, teaching, personality styles etc. The last included review (Kozhevnikov et al. 2014) was included as it represents the most recent attempt to categorize a number of style theories, and does this from quite another perspective than the previous works. In addition, the works all categorize style theories in different ways, which aided the purpose of developing the proposed taxonomy for categorizations of style theories. The included works cover a very long time range (i.e. 35 years), thereby also providing information on the development in the categorizations of styles theories over time.
Proposed taxonomy of categorizations
Type A. Co-ordinate categorization of style theories with reference to sorting
Categories are defined as separate co-ordinate categories (there is no hierarchical relationship between the categories), so that a sorting of the theories of styles into these categories is achieved with the categorization.
Type B. Hierarchical categorization of style theories with reference to taxonomy
Categories are hierarchically constructed around one or more key characteristics of the theories, so that with the categorization, a taxonomy in relation to which theories of styles may be categorized is set up.
Type C. Hierarchical categorization of individual styles across theories with reference to taxonomy
Categories are hierarchically constructed around several key characteristics of individual styles, so that a sorting of individual styles across theories into a notional over-taxonomy is achieved with the categorization, so to speak.